One of the first questions engineers ask when they begin designing a fluid-handling system is whether a pump can reliably handle a high-viscosity fluid. The answer is usually yes, but overall success is contingent on selecting the appropriate pump and optimizing the overall fluidic system for the intended application.
Image Credit: Fluid Metering, Inc.
In contrast to low-viscosity liquids, more force is needed to move viscous fluids through tubing, fittings, and pump components. If the system design has not considered these characteristics, flow restrictions can impede performance and lead to unnecessary stress being placed on the pump. Yet, rather than seeing viscosity as a limitation, it should be considered a key engineering parameter that drives pump selection, system layout, and operating conditions.
What is Viscosity?
Viscosity is the relationship between a fluid's resistance and flow. Low-viscosity fluids flow easily because their molecules glide over one another with relatively little resistance. These fluids usually pass quickly through tubing with little trouble or effort. High-viscosity fluids behave in the opposite way; they have slower flow rates and resist deformation.
This means a high-viscosity liquid may require additional force to be able to pass through a pumping system. With increased viscosity comes the elevated importance of ensuring proper system design. One of the first steps is understanding this relationship before selecting the right pump for reliable fluid dispensing of all viscosities.
How Viscosity Influences Pump Performance
Higher viscosity affects how the entire system is set up. Engineers should consider the system-component effect of higher viscosity when dealing with fluids of increased viscosity.
- Tubing: Greater flow resistance and higher pressure drop
- Pump inlet: Harder for fluids to enter the pump, which can starve the inlet
- Pump speed: High speeds raise mechanical stress and torque
- Flow rate: Higher flow rates become increasingly difficult
- System design: May necessitate temperature control or pressure assistance
These considerations underscore why it is crucial to carefully evaluate pump selection within the context of the entire system rather than simply as an isolated component.
Can FMI Pumps Handle High-Viscosity Fluids?
Yes, but pumping success is directly reliant on selecting the appropriate pump configuration for the specific application.
The most significant factor to consider is flow rate, as applications that demand very high flow rates may present greater challenges because viscous fluids naturally resist flow.
Instead of placing the focus solely on the pump, engineers should assess the following:
- Required flow rate
- Tubing selection
- Pump operating speed
- Inlet conditions
- Fluid temperature
Together, these variables have a considerable influence on overall pumping performance.
Engineering Best Practices
1. Increase Tubing Size
Using tubing that is not large enough to handle thicker viscosities creates unnecessary flow restrictions, meaning the fluid has a hard time even reaching the pump. Larger tubing offers a more direct flow path that lets viscous liquids pass more effectively through the system.
2. Reduce Viscosity with Temperature
Fluid viscosity can be managed and even decreased by heating the fluid, particularly on the inlet side, which also improves flow characteristics. For applications in which thermal management would be beneficial, FMI offers pump head options designed to help sustain a steady fluid temperature during pumping.
3. Use a Pressure-Fed Inlet
Pressure applied at the inlet allows viscous fluids to move through the tubing and into the pump head more efficiently. This additional boost can improve the system’s overall performance when handling more viscous liquids.
4. Operate at Lower rpm
Pump speed also impacts system performance. Setting the pump to run at 400 rpm or below, when appropriate for the application, can:
- Allow viscous fluids to move more effectively through the system
- Reduce stress on the pump and motor
Image Credit: Fluid Metering, Inc.
Common Mistakes When Pumping Viscous Liquids
Pumping performance can also be impacted by a number of common design decisions.
Avoid:
- Disregarding the benefits of temperature control for suitable applications
- Operating without inlet pressure when pressure feed offers an advantage
- Operating at exceedingly high pump speeds
- Tubing that is too small
Not taking these factors into consideration can place unnecessary strain on the system and reduce pumping efficiency.
Selecting the Right Pump for High-Viscosity Fluids
There is no single pump that can be said to be the optimal choice for every viscous fluid application. Pump selection is dependent on evaluating the complete operating environment, including:
- Fluid viscosity
- Required flow rate
- Tubing configuration
- Operating speed
- Temperature
- Inlet conditions
Taking all of these factors into consideration allows engineers to develop a fluidic system that supports reliable, repeatable operation.
The Bottom Line
When it comes to pumping high-viscosity fluids effectively, there are several engineering challenges to be considered; successful operations are dependent on the overall system design and pump configuration.
By carefully considering tubing size, operating speed, inlet pressure, and temperature at the beginning of the design process, engineers are able to improve the flow of highly viscous fluids and facilitate a more dependable system performance.
When evaluating a high-viscosity fluid application, Fluid Metering's engineering team supports its clientele by guiding clients toward the most appropriate pump configuration based on operating requirements and application goals.
This information has been sourced, reviewed, and adapted from materials provided by Fluid Metering, Inc.
For more information on this source, please visit Fluid Metering, Inc.